Vent Pipe Sealing

[BC Bus]

I am getting ready to run a black water tank vent pipe through the floor and up through the rood of the ol GMC 4108.   I'm sure you can provide me with ideas on seals and sealing to the outside roof, and vent caps, and size of pipe.

Thanks

Bill
Gresham, Or
4108 and MC 9

[Ace]

This has been beat to death but save yourself the worry of leaks and just run it out the top of the tank and then straight down thru the floor. Regardless of what people say that it can't be done, I'm still using mine after about 8 years and no smell or problems!

[bigjohnkub]

I agree with Ace.  5 years and no smell or other problems.
  Big John

[bevans6]

Y'all re-wrote the periodic table?  Methane is lighter than air, it rises.  It is trapped inside the tank unless there is a way for it to get out.  If you don't have a rising vent, then it either just accumulates or it gets out past the toilet seal into the bus.  

Your call on if that is good or not...

This is, btw, the synopsis of the "beat to death"...    

Brian

[bevans6]

To the question:  you can buy a purpose made vent pipe sealing flange at the RV store.  It seals to the roof with adhesive sticky tape and around the 1.25" pvc pipe and usually has a little cap or other topper to keep the rain out.  Some have venturi's that are supposed to suck a vacuum in the tank when driving, etc.  Lots of choice.  You can also get little fans to put in the vent line.  Iffy if they actually do anything but make you feel better...

Brian

[Ace]

Too funny but it is what it is

[bevans6]

Ace, my vent pipe runs into the rear wheel well.  It has yet to bother me enough to rise to the top of the fix-it list.  So I have yet to practice what I preach...      In self defense I can only say that the previous owner (a high school teacher, yet) ran it into the wheel bay...

Brian

[BC Bus]

I guess I didn't know there were so many opinions on this topic.   I have decided to definitely run mine up through the roof so I will go buy a flange and vent top and do it to it.  Not that hard to do so why not.

Thanks for your input.

Bill
Gresham, OR
4109 and MC 9

[Ace]

You Mean a real honest to goodness teacher changed the periodic table? Shame on him!

[Mex-Busnut]

I got two of these off of Ebay for less than $10, including postage.

[Brassman]

I used 3m 5200 sealant at the roof penetration. Don't have anything on the end of the pipe yet, except a temporary cap to keep the rain out during winter storage. No leaks. Just make sure the penetration hole is a close fit.

[Melbo]

I used a flange designed for use on metal roofs. It has a rubber boot that goes around the pipe and seals around the pipe and will move if necessary then seal  the perimeter with any adhesive that you like --- personally I like the polyurethane from PL that you can pick up at home depot.

HTH

YMMV

Melbo

[Bussman84]

Bill, I also went through the roof on our MC-9, our old bus had them just coming out the tank and then pointed down like Ace was talking never had a problem but it was a school bus conversion with lots of ground clearance. So I wasn't sure how it would work on the MCI since there isn't much ground clearance when parked and I didn't want the gas to get "trapped" under the bus where it might cause a stink sitting outside. I used 1.25 black ABS pipe through the roof cut a pretty snug hole everywhere the pipe went through the bus then siliconed around the pipe at each location and used a vent cap similar to what Dr.Steve posted the picture of, only I got the Galvinized metal ones from a local RV supply store about $5 bucks a piece one for the Black and one for the Gray, and used the RV strip caulk to seal where the cap screwed to the roof. So far so good, Hope this helps.

            Billy

[Bill 340]

well if you forget to dump the black tank,  AND YOU WILL someday. of the pipe comes out the bottom so does the overflo. where do you think the overflo goes if its roof vented...........  Just a thought, I have seen soap suds pouring out the top of RVs when they forgot to open the grey valve before doing laundry.  Our vent,    out the bottom this coach and the last

[eagle19952]

not the sharpest tac in the box...but without a p-trap or s-trap doesn't
it make sense that every time you get off the library stool (whether you like it or not) you are venting your black tank ?
And if you have a weepy seal then the black tank is continually venting....
And correct me if I am wrong but methane alone is harmless....unless of course you are suicidal or homicidal....